1. Field of the Invention
This invention relates to a hydraulic buffer and, more particularly, to a hydraulic buffer of variable damping force type suited for a buffer of a suspension for an automobile.
2. Description of the Prior Art
There is disclosed a variable damping force type hydraulic buffer provided with a cylinder, a piston and a piston rod, in which a bypass for affording communication between two liquid chambers defined at both sides of the piston and a regulating valve capable of being operated from the outside are provided in addition to a valve mechanism which is inherently installed in the piston to generate a damping force and the damping force is regulated by opening or closing the bypass with the regulating valve (for example, Japanese Utility Model Public Disclosure (KOKAI) No. 85285/79). In the hydraulic buffer, since it is constituted such that liquid passes through same bypass in the extension and contraction of the piston rod, the ratio of the damping force in the extention to that in the contraction of the piston rod cannot be changed.
A hydraulic buffer disclosed in the Japanese Utility Model Public Disclosure (KOKAI) No. 191448/83 (hereinafter referred to as improved hydraulic buffer) has an inner chamber formed in the piston rod and communicating to one liquid chamber and two oil paths permitting the inner chamber to communicate to the other liquid chamber. A check valve is provided in one oil path, while a shutter capable of regulating individually two oil paths is disposed in the inner chamber to be operated from the outside. By the improved hydraulic buffer can be changed the ratio of the damping force in the extension to that in the contraction of the piston rod to increase the freedom of regulating the damping force.